Portable system and method for processing waste to be placed in landfill

ABSTRACT

A portable system and method for processing waste to be solidified and placed in an active cell of a landfill. A portable pugmill is moveable adjacent an active cell of a landfill; and portable devices, which may be mounted on sleds or trailers, may be used for feeding the pugmill with waste to be solidified into a landfill-ready state. The waste may be fed to the pugmill without the need for long-term waste storage devices, and avoiding substantial delays between discharge of the waste from trucks to the pugmill-feeding steps.

BACKGROUND OF THE INVENTION

The present invention relates to systems and methods for treatinglandfill waste using a portable pugmill system.

Operating landfills are provided with liquid and solid waste on aconstant basis. Some of these waste materials must be further processedbefore they can be legally entombed within a landfill. This processingmay include mixing waste liquids, sludges and other semi-solid wasteswith absorbent materials or other solid (dry) wastes (termed here “wastesolidification operations”), before the resulting mixture issufficiently devoid of any “free liquids” so that it may be legallydisposed within an active landfill cell. Examples of liquid wastes thatmay be treated by the present invention include, but are not limited to,various approved liquid wastes, landfill leachate, or surface water fromthe landfill or off-site locations.

Currently, the required waste solidification operations may be performedin “batch” processing techniques using open-top, leakproof containerslocated in an area of the landfill that has both a certified liner andan operating leachate collection system. This is a time-consuming andinefficient process which requires a large portion of the landfill thatcould otherwise be devoted to stored waste.

Another processing technique to achieve sufficient waste solidificationthat has been used in the past has been a large, expensive fixed system,using a processing plant with a fixed pugmill fed by a fixed, largeoverhead silo not adapted to be portable. No discharge conveyor is used;instead, a truck drives under the pugmill, which drops the solidifiedwaste into the truck, for delivery to the landfill.

Pugmills used in the systems of the present invention can weigh 6 tonsor more. Horsepower requirements for the required multiple motors (for,e.g., pugmill, conveyors, generators, etc.) may be 300-350 hp or more.Also, the area of a landfill typically comprises low-grade, unstablematerials such as wet clay with little bearing strength, and spongymunicipal solid waste (residential garbage). Further, one end of each ofthe conveyors is typically ten feet or more off the ground. Theseissues, including issues of alignment, vibration control, leveling,stability in wind, deterioration in rain and snow, adequate 3-phaseelectrical power source, and practicality of maintenance, which canroutinely be handled by a fixed (non-portable) system, provide manyreasons not to attempt to make such a processing system portable.

If one were thinking of changing a fixed processing system into aportable processing system, a natural approach would be to mount thesystem on wheels for ease of movement. However, landfill conditions makesuch an approach problematic. For example, a landfill typically providesvariable, uneven terrain, which may include wet clay and spongymunicipal solid waste. In wet conditions, the terrain is conducive tomud. Such conditions may make it difficult if not impossible to wheelconveyors or other equipment, and outriggers may be needed to stabilizethe equipment.

Large capacity solid storage systems are also easily provided with afixed system (e.g., using a silo), which is problematic if the system isto be made portable. Such large capacity, tall silos, for example,cannot easily be secured against wind loads, and are difficult to move.For example, if a system were to be made portable, it must be typicallycapable of processing 1-2 truckloads (25 tons/load) very rapidly (about15 minutes/load, while the truck waits) without using tall verticalsilos as used in fixed systems, as such silos cannot be safelytransported in landfill conditions. By comparison, a fixed system withtall vertical silo(s) may take about 45 minutes to pneumatically load(per truck) and then another 15 minutes/truck to feed the pugmill andprocess the material.

A test for determining whether a liquid waste solidification processproduces waste which can be legally entombed within a landfill is knownas the Paint Filter Test (“the PFT”). The PFT is used to simulate thebehavior of liquids contained in sorbents to be placed in landfills. Thepurpose of the PFT is to determine if excess liquids will be releasedfrom containerized wastes. The basis for the test derives from an EPArule (Section 3004 (c) (2) of HSWA), which prohibits the placement ofbulk or containerized liquids in landfills. The PFT is a simple, easy toconduct test that is relatively inexpensive to perform, and that hasbeen used to determine the presence of free liquids in bulk orcontainerized waste since 1985. It consists of placing a sample(normally 100 ml or 100 g) into a conical paint filter (mesh number 60).The paint filter is suspended from a tripod or ringstand for fiveminutes. If any portion of the material passes through and drops fromthe filter in this time, the material is deemed to contain free liquidsand cannot be disposed of in a landfill.

Another feature that can render material unsuitable for a landfill isdust. Various regulations monitor the amount of dust associated withlandfill materials, given the danger to landfill operators and personnelin the vicinity of a landfill due to dust. It has been determined thatdust regulations will be satisfied by a relatively simple test: thematerial to be placed in a landfill must be in the range of about atleast 5% (20:1 solids-to-liquid ratio by weight)-20% (4:1solids-to-liquid ratio, by weight) moisture by weight. Typically, this“moisture test” is determined by a laboratory, which weighs thematerial, then bakes off the moisture and weighs it again. However, anexperienced landfill operator can typically determine whether themoisture test will be met by visual observation, coupled with periodiclab tests. If dust becomes an issue, the operator can simply add liquidto the pugmill.

SUMMARY OF THE INVENTION

The objects mentioned above, as well as other objects, are solved by thepresent invention, which overcomes disadvantages of prior systems andmethods, while providing new advantages not previously associated withthem.

The present invention may utilize one or more solid material feedconveyors, a communicating portable pugmill type liquid/solid mixingunit, and a receiving conveyor for the solidified mixture dischargedfrom the pugmill. The system of the invention enables the more effectiveand efficient mixing of waste liquids with dry material in order toproduce a solidified product suitable for disposal in an active landfillcell. The system enables the landfill to process a wider range of wastematerials, such as certain types of coal combustion waste that haveproven difficult to dispose of in a typical landfill active cell.Additionally, pugmill processing greatly reduce fugitive dust that mightotherwise be released from the waste as it is disposed in the landfillcell. Such dry coal combustion wastes typically consist of all forms offly ash, bottom ash and other pollution control coal combustionby-products that are amenable to solidifying water-based liquids.

In a preferred embodiment of the invention, a portable system forprocessing waste so that it can be made landfill-ready is provided. Thewaste initially contains free liquids and requires the addition ofsolids in a solidification process. The system includes a portablepugmill which can be moved to various locations atop an active cell of alandfill; and one or more portable devices for facilitating periodicfeeding of the pugmill with waste to be solidified into a landfill-readystate. The waste may be discharged from a truck to the one or moredevices, and then may be fed to the pugmill without using long-termstorage devices, and avoiding any substantial delay between wasteunloading from the trucks and feeding of the pugmill.

In preferred embodiments, the portable conveying devices may be aconveyor for transporting solids to the pugmill, and a liquid pump fortransporting liquid or sludge waste to the pugmill. A live floor trailermay be used to provide waste solids to the conveyor. Alternatively,solid waste may be transferred from a pneumatic truck to a portableshort silo and then directly fed to the pugmill through an airlock.

To facilitate their mobilization and portability, the pugmill and theportable feed and discharge devices may be mounted on one or morestructural sleds suitably designed to move over variable, nonuniform anduneven landfill terrain. (As discussed below, instead of structuralsleds, although this may be less preferred, such devices may be mountedon trailers, or comprise generic wheeled structures.)

A portable generator is preferably used to provide power to the pugmilland to the portable devices. The pugmill may have a variable frequencydrive.

Preferably, the waste is tested for compliance with the PFT test beforebeing placed in the landfill.

As a working example, the waste may include coal ash, with about a 1:1weight ratio of coal ash to water-based liquids mixed within thepugmill. The waste may also include scrubber waste, in which about a 2:1weight ratio of scrubber waste solids to water-based liquids may bemixed within the pugmill.

Preferably, for the solids component of the waste, the system does notseparately store the solids component. The pugmill can be fed with alive floor trailer and feed conveyor, or with a portable silo straddlingthe pugmill. The portable silo may be fed with the solids componentusing pneumatic trailers.

Dust hoods applying negative induction pressure within the portable feedconveyors may be used to limit dust generated there.

An electronic control panel and an automatic electronic measuring systemmay be used, to allow an operator to specify solid and liquid ratios andflow rates into the pugmill.

Landfill-ready waste processed by the pugmill(s) may be discharged tohaul trucks for depositing in an active cell of the landfill, or may bedischarged directly into an active cell of the landfill.

A method for processing waste so that it can be made landfill-ready alsoforms part of the present invention. The waste may initially containfree liquids and require a solidification process. One or more portablesolids feed devices (conveyors and/or short silos) may be provided, fortransporting a solids component of the waste to a portable pugmill. Oneor more portable liquids feed devices may also be provided, fortransporting a liquids component of the waste to the portable pugmill.The solids and liquids components may then be mixed within the pugmillat one or more predetermined, desired ratios, so that the mixture islandfill-ready. The landfill-ready waste may then be transporteddirectly from the pugmill into haul trucks for depositing into an activecell of the landfill, or may be discharged directly into the activecell.

The portable solids feed devices may include conveyors, and the portableliquids feed devices may include liquid pumps. These devices may each bemounted on trailers or sleds or bearing pads, or wheeled structuraldevices (e.g., devices including wheeled columns supporting theconveyors, pugmill and silo). The solids component of the waste may bedischarged from trucks to the portable solids feed devices and then fedto the pugmill without any substantial delay between the trailerunloading and pugmill feeding steps. A portable silo straddling oradjacent the pugmill may be provided. The silo directly feeds the solidscomponent, without storage, through an airlock into the pugmill. Thepugmill and the portable solids and liquids feed devices may be mountedon one or more sleds or trailers or bearing pads or wheeled structuraldevices. The portable solids conveyors may include dust hoods applyingnegative induction pressure to limit dust generated there. Samples ofthe waste may be periodically tested for compliance with the PFT andmoisture tests.

DEFINITION OF CLAIM TERMS

The terms used in the claims of the patent are intended to have theirbroadest meaning consistent with the requirements of law. Wherealternative meanings are possible, the broadest meaning is intended. Allwords used in the claims are intended to be used in the normal,customary usage of grammar and the English language.

“Landfill-ready” or “landfill-ready waste” means waste that can belegally placed in a landfill.

“Portable pugmill” means a pugmill mounted on or supported by a sled ortrailer or wheeled structural device (e.g., a device including wheeledcolumns supporting the conveyors, pugmill and silo.

“Portable silo” means a silo mounted on or supported by a sled ortrailer or wheeled structural device, or mounted on steel bearing padsthat rest directly on the landfill active cell and have no fastenerstied to the cell.

“Sludge” means waste with a substantial free liquids component.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features which are characteristic of the invention are setforth in the appended claims. The invention itself, however, togetherwith further objects and attendant advantages thereof, can be betterunderstood by reference to the following description taken in connectionwith the accompanying drawings, in which:

FIG. 1 is a perspective view of one preferred embodiment of the presentinvention;

FIG. 2 is an enlarged view of the portion of the system circled on FIG.1;

FIG. 3 is a sectional view taken along reference line 3/3 of FIG. 2;

FIG. 4 is a perspective view of an alternative embodiment of the presentinvention; and

FIG. 5 is a perspective view of another alternative embodiment of thepresent invention.

The components in the drawings are not necessarily to scale, emphasisinstead being placed upon clearly illustrating the principles of thepresent invention. In the drawings, like reference numerals designatecorresponding parts throughout the several views.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Set forth below is a description of what are believed to be thepreferred embodiments and/or best examples of the invention claimed.Future and present alternatives and modifications to this preferredembodiment are contemplated. Any alternatives or modifications whichmake insubstantial changes in function, in purpose, in structure, or inresult are intended to be covered by the claims of this patent.

Referring now to FIG. 1, a preferred embodiment of the portable systemof the present invention for solidifying sludge waste and transportingit either to haul trucks for depositing to an active cell of a landfill,or for direct discharge into the active cell, is shown and generallyreferred to by reference numeral 10. With system 10, dry solids may betruck-fed onto an intake conveyor 15, and discharged into pugmill 20,such as a double-paddle mixing pugmill having blades 20 a set onmultiple rotor shafts 20 b. Simultaneously, a liquid pump (not shown),such as a 3-inch or 4-inch diameter liquid pump, may be used to feedliquid/sludge waste into pugmill 20. The liquid pump may have flexibleinlet piping to connect to liquid waste storage containers which may bemounted on a tanker trailer, for example (not shown). The liquid pumpmay also have flexible outlet piping (with a flow-restricting valve, notshown, to control flow rate) to connect to pugmill 20, to deliverliquid/sludge waste stored in the tanker trailer(s) (e.g., liquid waste,leachate or water) to pugmill 20. The flow rate of the liquid feedshould be sufficient to control dust, or to wet the dry solids to thepoint where the mixture will meet the Paint Filter Test (“PFT”)requirements. The resulting solidified waste, suitable for landfillstorage, may then be discharged from outtake conveyor 25 into a haultruck, or directly into an active cell 30 of a landfill. As examples,conveyor 15 may be about 12-feet in the air at its highest point,whereas conveyor 25 may be about 15-feet in the air at its highestpoint.

Approximate mixing ratios have been developed that will pass therequired PFT test for two common solid feed materials that may beprocessed by the present invention: (a) coal ash (1:1 by weight, solidsto water-based liquids); and (b) scrubber waste (2:1 by weight, solidsto water-based liquids). (In a coal power plant, combustion productsfrom the stack are “scrubbed,” removing sulfur and other pollutants,using components such as calcium carbonate and gypsum.) The pugmillsolid and liquid feed rates may be adjusted in order to provide theseratios.

Other solid feed materials may be used, of course, and different weightratios may be developed. Non-limiting examples of solid feed materialsthat may be treated by the present invention include: scrubber wastefrom scrubber systems operating on other combustion products (e.g.,cement kilns, etc.); sawdust; auto fluff (shredded, non-metal portionsof automobiles); by-products from the coal combustion, such as fly ash,bottom ash; diapers, or any other solidification materials approved bythe permit, etc.

Referring again to FIG. 1, solidified waste discharged from pugmillmixer 20 may be permitted to drop onto receiving conveyor 25, which canbe configured to deposit the material directly into a waiting haultruck, or directly into an active cell of a landfill. Samples of thematerial discharged from the pugmill mixer may be periodically obtainedand subjected to a Paint Filter Test to verify that no free liquids arepresent.

As a non-limiting example, the conveyors and pugmill may be obtainedfrom Pugmill Systems Inc. of Tennessee, or other manufacturers in theindustry.

In a particularly preferred embodiment of the present invention, thepugmill, short silo and conveyors may be mounted on sleds, such asstructural steel sleds 60, providing both the ability to transport thisequipment, while also the ability to do so in a stable manner, despiteoften the presence of difficult (uneven, muddy, etc.) landfill terrain.A sled can also more easily be leveled than wheeled conveyors.(Alternatively, although less preferred, a trailer may be used to mountthe pugmill, short silo and conveyors. As discussed below, bearing pads(such as for the portable silo) or wheeled structural devices may alsobe used.)

Preferably, the sled is flexible enough to accommodate uneven andunstable landfill terrain, while strong and stiff enough to hold theoperating equipment in a stable manner under dynamic loading duringoperation. Further, the sled frame must be able to be easily leveledusing, e.g., timbers at different frame locations, as dictated by theground conditions of the final set-up, without inducement of excessivestress.

Ancillary equipment for the system may include a portable trailer (or,alternatively, sled-mounted or bearing-pad mounted) which may be used tomount one or more diesel-powered generators, such as with a capacity of200-300 KW (460/480V 3-phase) or larger, liquid storage containers, andan electric-powered (e.g., 3-4 inch diameter) liquid pump. The generatorcan be electrically connected to the pugmill system control panel, whichthen powers all necessary electric equipment.

A control panel (not shown) may be used to control the speed/rate ofintake conveyor 15, pugmill 20 and discharge conveyor 25, and otherancillary equipment which may be used, such as a silo airlock, a siloaerator and a silo dust-house vibrator (discussed below).

Depending on the waste being landfilled, some landfill customers mayrequire delivery of their waste in trucks with live floor trailers,which then deposit the waste onto an inclined feed conveyor (feed mode Aor “FMA”) leading to the pugmill. (One live floor trailer which may beused is the 45-foot Aluminator trailer (4266542) manufactured by ValleyFarm Industries of Nebraska, which allows the discharge of solids withminimal dust generation.) Other landfill customers may have differentwaste which requires its delivery via pneumatic trucks, which may thenfeed the waste into short-silo storage (feed mode B or “FMB”), which inturn gravity-deposits the waste into the pugmill, using the airlock tocontrol feed rate. In FMB, for example, one to four pneumatic trucks maybe used to unload solids simultaneously for immediate processing.(Again, no long-term material storage is required).

Referring to FIG. 4, an embodiment in FMA mode is shown. Here, a truckwith a live floor trailer 65 may be positioned, for example, anddelivers solid waste down chute 68 onto conveyor 15, which delivers thesolid waste to pugmill 20, where it may be mixed with liquids (notshown) and the resulting waste suitable for a landfill may be deliveredby conveyor 25 either to a haul truck for delivery to an active cell 30of the landfill, or discharged directly into an active cell 30 of thelandfill, for example.

Referring to FIG. 5, an embodiment in FMB mode is shown. A shortportable silo 70 may be employed to straddle or stand beside pugmill 20(portable structural components for holding the silo over the pugmillare not shown), allowing unloading and feeding solids using pneumatictrucks (not shown), into the silo, and then from the silo into thepugmill. A pumper truck 50 can also deliver sludge or water-based wasteinto the pugmill, as shown.

Instead of resting on a transportable sled or a trailer, portable silo70 may rest on bearing pads (e.g., flat steel plates), which restdirectly on the active cell of a landfill. When it needs to be moved,portable silo 70 may be lifted and dropped by a crane or other device,or it may be dragged on its bearing pads. Portable silo 70 has nofasteners (such as anchor bolts) tied to the landfill. However, thecolumns supporting the portable silo may be welded to the bearing pads.Alternatively, a wheeled structural device may be used to support thesilo.

Preferably, the present invention can accommodate either of the twomodes FMA or FMB. The system solid feed mode may preferably be switchedback and forth between FMA and FMB, at the operator's discretion, takingnegligible time to do so. For example, if in FMA mode and the operatordesires to switch to FMB mode, power to the feed conveyor (intake topugmill) may be switched off, and a chute may be opened between theshort silo and the pugmill; now, hose/pipe fittings for one or morepneumatic trucks may be connected to the silo intake nozzle(s), and theshort silo airlock, dusthouse equipment and vibrators may be powered on;and finally the pneumatic truck systems may be started, conveying thesolids into the short silo, which then gravity-feed into the pugmillthrough the airlock which controls the feed rate.

To further eliminate dust, a dust hood may be provided that fits overfeed conveyor 15, while allowing the trailer to back into the dust hood.The dust hood may be under induction draft fan negative pressure, sothat any dust generated during solids unloading and conveying may bedrawn into covered conveyor 15. A manual or automatic shutoff may beprovided in the dust hood if sensors determine that dust guidelines(such as the 5-20% moisture content test, by weight) are not being met.

It is believed that use of the system disclosed here will generate anegligible amount of dust in the sealed feed conveyor, pug mill anddischarge conveyor. As some dust may be generated during truck unloadinginto the feed hopper, if needed a negative pressure dust-hood with aconventional induction draft blower may be provided, as discussed abovewhich the truck can back into. Any dust inside the dust-hood can beconveyed to an opening in the feed conveyer.

An automatic solid and liquid electronic measuring and control systemcan be readily engineered, such as by using microprocessors and motorsavailable from Allen Bradley of Milwaukee, or other manufacturers, andusing appropriate electronic sensors, to provide real-time feed rates tothe pugmill of solid and liquid waste streams. Additionally, theelectronic measuring system may also be used to provide real-timepugmill product discharge flow rates and the percentage make-up ofliquids and solids in the waste discharge. Using these enhancements, aclosed loop control system may be provided, in which a single operatorcould specify the desired liquid/solid ratios, by weight percentage, ofthe mixture from the pugmill, and the feed conveyor rate (i.e., beltspeed) and liquid waste flow rate (flow valve) could be adjusted toproduce these desired liquid/solid ratios. Only occasional sampling forPFT compliance would then be required as the waste is landfilled.

Electrical switch gear (panel boxes, disconnects, breakers, etc.) may beobtained from Square D of Illinois (now owned by Schneider Electric), orother manufacturers. The electric motors, for turning the dual pugmillshafts, for driving the discharge and feed conveyor belts, for theportable silo motors, and for the fan motor for driving the dust hoodfan, may be obtained from General Electric (Indiana), or othermanufacturers. The GE pugmill motors turn about 1800 rpm, and thepugmill shafts turn about 30 rpm, using a speed reducer which may beobtained from Dodge/Baldor (Arkansas). The variable frequency drive forthe pugmill may be obtained from Danfoss (Denmark). The liquid pump(s)referenced above may be obtained from any of the following sources:Godwin (New Jersey); Wacker (Wisconsin); or Gorman/Rupp (Ohio). Anelectrical generator(s) may be obtained from Caterpillar TractorCompany. The short, portable silo referenced above may be obtained fromBelgrade (Minnesota). The electronic controls may be obtained from AllenBradley (Wisconsin), as described above. These items are available fromalternative manufacturers as well.

In the preferred embodiment disclosed here, exemplary electrical(horsepower, “HP”) requirements may be as follows: first pugmill motor(50 HP); second pugmill motor (50 HP); feed conveyor motor (20 HP);discharge conveyor motor (20 HP); silo air-lock motor, if used (5 HP);silo aerator motor, if used (4 HP); silo dusthouse vibrator, if used (1HP); pump (up to 50 HP). The total power requirements may be up to 250HP.

A person of ordinary skill in this art will now readily appreciatevarious advantages of the present invention. The system can be madeentirely portable, enabling it to be located anywhere over a landfillarea that has both a certified liner and an operating leachatecollection system, including an active cell face. This enables thelandfill operator to process the final waste product at a locationclosely adjacent to its final destination. Also, once initially erected,the systems disclosed may take no more than 1-2 days to move and set-upat a new location in the landfill. Additionally, in a preferredembodiment, the system does not require any dry material storagecapacity; dry solids may be processed as they are unloaded from eitherlive-floor or pneumatic tractor trailers.

If necessary, to alleviate equipment layout challenges at the selectedwaste solidification location, the feed conveyor can be rotated andoperated up to 90 degrees in either direction from the straight-onconfiguration shown in FIG. 1.

The system disclosed here will accept up to 25 tons of dry combustionwaste which may include coal ash, bottom ash, or scrubber waste, from alive-floor transport trailer, and process it in a relatively shortperiod of time, such as the about 15-minute unloading time (300 tph), ina nearly dust-free condition. The dry solids will be mixed with up to 25tons of liquid, also in the same short period of time of about 15minutes (300 tph=1200 gpm). Of course, the system disclosed here can bescaled up or down to process greater or lesser amounts of liquid waste.

Should insufficient dry coal combustion waste be available to mix withincoming liquid wastes, any permit-approved solid/special waste orpermit-approved solidification material (i.e., currently permittedreagents, absorbents and purchased solidification materials) may be usedfor pugmill liquid waste solidification. Landfill liquid waste, leachatewaste or lakewater may be transported to the pugmill via a tanker truck.

If it is desired to deliver solids via multiple pneumatic trucks, thesystem may be retrofitted with a short upright silo, for example, thatincludes a powered air-lock, aerator, and dust-house vibrator. The silomay be installed to straddle or mount beside the pugmill, and may befilled by one to four pneumatic trucks simultaneously. Each truck,holding for example 20-25 tons of solids, can deliver their solids tothe silo in about 30-45 minutes. If this feature is used, this willprovide two modes of feeding the pugmill that can be easily switchedback-and-forth.

The above description is not intended to limit the meaning of the wordsused in the following claims that define the invention. Persons ofordinary skill in the art will understand that a variety of otherdesigns still falling within the scope of the following claims may beenvisioned and used. As another example, dust hoods and otheraccessories are optional, as indicated above. It is contemplated thatthese additional examples, as well as future modifications in structure,function, or result to that disclosed here, will exist that are notsubstantial changes to what is claimed here, and that all suchinsubstantial changes in what is claimed are intended to be covered bythe claims.

I claim:
 1. A portable system for processing waste so that it can bemade landfill-ready, the waste initially containing free liquids andrequiring addition of solids in a solidification process, comprising: aportable pugmill which can be moved to various locations atop an activecell of a landfill; and one or more portable conveying devices forfacilitating periodic feeding of the pugmill with waste to be solidifiedinto a landfill-ready state, wherein the one or more portable conveyingdevices comprise a portable short silo mounted on one or more bearingpads that rest directly on the landfill active cell and have nofasteners tied to the cell, and wherein waste solids are discharged froma pneumatic truck to the portable short silo and then directly fed tothe pugmill, without using long-term storage devices and avoiding anysubstantial delay between the truck-discharge and pugmill-feeding steps.2. The system of claim 1, wherein the one or more portable conveyingdevices further comprise a conveyor for transporting solids to thepugmill, and a liquid pump for transporting liquid or sludge waste tothe pugmill.
 3. The system of claim 1, wherein the one or more portableconveying devices further comprise a live floor trailer for use inproviding waste solids to a feed conveyor.
 4. The system of claim 1,wherein the one or more portable conveying devices are mounted on one ormore transportable sleds.
 5. The system of claim 1, further comprising aportable generator to provide power to the pugmill and to one or moreportable feed and discharge devices.
 6. The system of claim 1, whereinthe pugmill comprises a variable frequency drive.
 7. The system of claim1, wherein the waste is tested for and complies with the PFT test beforebeing placed in the landfill.
 8. The system of claim 1, wherein thewaste includes coal ash, and a weight ratio of coal ash to water-basedliquids mixed within the pugmill in the range of about 1:1 to 20:1. 9.The system of claim 1, wherein the waste includes scrubber waste, and aweight ratio of scrubber waste solids to water-based liquids mixedwithin the pugmill in the range of about 2:1 to 20:1.
 10. The system ofclaim 1, wherein the waste includes a solids component, and wherein thesystem does not separately store the solids component.
 11. The system ofclaim 1, wherein the waste includes a solids component, and furthercomprising a portable silo adjacent the pugmill, wherein the siloreceives the solids component, and the solids component is fed from thesilo into the pugmill.
 12. The system of claim 1, wherein solidscomponents from trailers are discharged to a feed conveyor, and thenintroduced to the pugmill.
 13. The system of claim 1, further comprisinga control panel and an automatic electronic measuring and control systemallowing an operator to specify solid and liquid ratios and flow ratesinto the pugmill.
 14. The system of claim 1, wherein the landfill-readywaste is discharged directly into an active cell of the landfill. 15.The system of claim 1, wherein the one or more portable devices compriseone or more portable solids conveyors, and further comprising one ormore dust hoods associated with the one or more conveyors, the dusthoods applying negative induction pressure to limit dust generated bythe one or more conveyors.
 16. A portable system for processing waste sothat it can be made landfill-ready, the waste initially containing freeliquids and requiring addition of solids in a solidification process,comprising: a portable pugmill which can be moved to various locationsatop an active cell of a landfill; and one or more portable conveyingdevices comprising a conveyor for transporting solids to the pugmill,and a liquid pump for transporting liquid or sludge waste to thepugmill, for facilitating periodic feeding of the pugmill with waste tobe solidified into a landfill-ready state, without using long-termstorage devices and avoiding any substantial delay between thetruck-discharge and pugmill-feeding steps, and wherein the conveyor andthe pugmill are mounted on one or more transportable sleds.
 17. Thesystem of claim 16, wherein the one or more portable conveying devicesfurther comprise a live floor trailer for use in providing waste solidsto a feed conveyor.
 18. The system of claim 16, wherein the one or moreportable conveying devices comprise a portable short silo mounted on oneor more bearing pads that rest directly on the landfill active cell andhave no fasteners tied to the cell.
 19. The system of claim 16, whereinthe waste includes a solids component, and further comprising a portablesilo adjacent the pugmill, wherein the silo receives the solidscomponent, and the solids component is fed from the silo into thepugmill.
 20. A portable system for processing waste so that it can bemade landfill-ready, the waste initially containing free liquids andrequiring addition of solids in a solidification process, comprising: aportable pugmill which can be moved to various locations atop an activecell of a landfill; and one or more portable conveying devices mountedon one or more transportable sleds for facilitating periodic feeding ofthe pugmill with waste to be solidified into a landfill-ready state, thewaste being discharged from a truck to the one or more conveying devicesand then being fed to the pugmill without using long-term storagedevices and avoiding any substantial delay between the truck-dischargeand pugmill-feeding steps.
 21. The system of claim 20, wherein the oneor more portable conveying devices comprise one or more of thefollowing; a conveyor; a live floor trailer; and a short silo.